By Ralph Kalal

When choosing among replacement batteries, the freshest battery with the largest reserve capacity is the better choice. Also, of course, the battery must have the correct physical dimensions and have a cold cranking capacity that meets the needs of your climate. Here’s what the specifications mean:

“Cold Cranking Amps” (CCA) 

CCA is the number of amps that the battery, when fully charged, can discharge for thirty seconds at 0 degrees F, while retaining voltage of 7.2 volts or above. This is not the same as “cranking performance amps” (CA), “marine cranking amps” (MCA), or “hot cranking amps” (HCA), all of which measure the cranking power of a battery at temperatures above 0 degrees f.  

A vehicle manufacturer normally sets a CCA specification for the vehicle battery. If the vehicle will be operating in cold climates, you may wish to exceed that specification. In warm climates, however, there is no need to exceed the manufacturer’s specification for CCA.

“Reserve Capacity” (RC)

This is the number of minutes at 80 degrees F that the battery can be discharged, at a rate of 25 amps, and maintain a voltage of 10.5 or more. Basically, it measures the ability of the battery to supply power to the car if the alternator is not functioning. A battery that has been discharged to a voltage of 10.5 is considered fully discharged.

“Group Number”

This refers to the physical dimensions of the battery and the type and placement of its terminals. The numbering system was established by an industry trade group, the Battery Council International. The group number can be either a two-digit number, such as 75, or a two-digit number followed by one or two letters, such as 58R.  

Group number 75 is most common to General Motors products; 65 applies most frequently to full-size Fords, Mercury’s, and Lincolns; 34 to Chrysler products; and 35 to Hondas, Toyotas, and Nissan products. Additionally, batteries may be labeled with two numbers, such as 34/78 to indicate the battery will meet the specifications of either group.  

Batteries differ substantially in size and placement of the terminals. A battery can be too tall or too wide to fit into the car. Even if it fits, if the terminals are not placed correctly, the battery cables may not be long enough to connect to the battery. Buying a battery of the proper group number prevents those problems.

“Amp/Hour Rating”:

The concept behind this number is related to the “reserve capacity,” but figured from the other end: the amp/hour rating states the number of amps that can be produced by the battery if discharged at a constant rate for 20 hours without dropping to 10.5 volts. In other words, if a battery has an amp/hour rating of 75, it would produce 3.75 amps per hour for 20 hours. This number is less relevant to battery performance than it is to recharging: a battery should not be recharged at a rate that exceeds one-tenth the amp/hour rating.

Is it inside the car?

Many automobile manufacturers now locate the battery away from the engine compartment, either in the trunk or under the back seat in the passenger compartment. This improves weight distribution, reduces the battery’s exposure to heat, and makes it easier to locate other components within the engine compartment. A number of vehicle manufacturers have taken this approach, including BMW, Cadillac, Mazda (Miata), and Toyota (Prius).

If a replacement battery is to be located inside the car, it must either have external venting or be of a type that does not produce hydrogen gas. This can substantially limit the available options when replacing a battery. For example, Mazda locates the Miata’s battery in the trunk. An “absorbent glass mat” (AGM) battery manufactured in Japan by Panasonic is original equipment, but it is not available as a replacement battery in the United States. Only a few independent U.S. battery manufacturers, including WestCo Battery Systems, make and market a replacement for the Miata OEM battery.

If the original equipment battery was located inside the car and was a wet cell battery, it has an external vent on the battery that fits into a ventilation system tube. Any replacement wet-cell battery must have the same vent and be connected to the same tube. As an alternative to a replacement wet-cell battery, it may be possible to use an AGM battery because AGM batteries ordinarily do not emit hydrogen gas during vehicle operation.   
   
Will the Car Sit for Long Periods of Time?

Batteries need to be kept charged. When a battery sits in a car that isn’t driven often, such as a collector car or a Corvette in wintertime Wisconsin, the battery may discharge over time. That’s bad for the battery, and can kill an AGM battery.  

There are two ways of dealing with this. One is a Battery Tender (online at batterytender.com) or equivalent device, which is a small monitoring battery charger that will keep the battery fully charged (but not overcharged) and costs about $50. The advantage of this device is that the battery continues to supply current to the various memory systems in the car.

Another choice is a battery that you can turn off: the DieHard Security battery has an in-built storage mode that can be set to disconnect the battery from the electrical system without removing the battery from the car. The DieHard Security costs about $60 more than a comparable DieHard battery, but you also get a small remote to activate the batterie’s various features. The features a power saver mode that guards against battery drain should the lights inadvertently be left on and several anti-theft features. Of course, if you lose the remote...

Who Really Makes It & When Did They Make It?
 
Most automotive batteries made in America are manufactured by one of two companies: Johnson Controls, Inc. or Exide Technologies. The dominant replacement market brand names, Interstate and DieHard, are both Johnson Controls products, as is the Optima brand.  Exide Technologies markets batteries under the Exide, and NASCAR Select brand names, and has manufactured the Champion brand, as well. However, Champion batteries are now manufactured by Johnson Controls. The other large domestic battery manufacturer, Delphi Corporation, sold its automotive battery business to Johnson Controls in 2005.  

Though a particular battery’s manufacturer can be identified though a manufacturer’s code number stamped into the battery’s case, here’s a short list of what’s made by whom:


 Brand  Manufacturer
 ACDelco   
 Johnson Controls
 Advance Auto   
 Johnson Controls
 AutoCraft Johnson Controls
 Autolite  Exide
 AutoZone  Johnson Controls
 Bosch  Johnson Controls
 Champion  Johnson Controls
 Costco  Johnson Controls
 Delco  Johnson Controls
 Delco-Remy   
 Exide
 DieHard  Johnson Controls
 Duralast  Johnson Controls
 Duralast  Johnson Controls
 Equalizer  Johnson Controls
EverStart (Wal-Mart) Exide or Johnson Controls, depending on model
 Firestone  Johnson Controls
 Interstate  Johnson Controls
 Marathon  Exide
 Motorcraft  Johnson Controls
 NAPA  Exide
 Optima Johnson Controls
 Orbital  Exide
 Pep Boys  Johnson Controls
 Sears Exide or Johnson Controls, depending on model
 
 Wal-Mart  Exide or Johnson Controls, depending on model

There is also a date code showing when the battery was manufactured. This is usually on a sticker attached to the battery or stamped into its case. It is a letter/number code. The standard convention is that the letter is the month of manufacture, alphabetically A through M but omitting I, with A being January and M being December. The number is the last digit in the year of manufacture. So, C6 is March 2006.

There are, however, some exceptions to this nomenclature. On Delco batteries, the arrangement was reversed: year first, then month. Exide batteries often bury the month/year designation in a larger number, so it is usually the fourth and fifth characters in that number.

battery